1. Let $\vec F = (-y,x+y)$ and $C$ be the straight line segment from $(3,0)$ to $(0,2)$.
    • Set up the work integral $\ds\int_C Mdx+Ndy$.
    • Set up the flux integral $\ds\int_C Mdy-Ndx$.
  2. Set up an integral formula to find the average value of $f(x,y,z)=x^2+y^2+z^2$ along three coils of the helix $\vec r(t) = (4\cos t,4\sin t,3t)$ starting at $t=0$. Recall that average value is given by $\bar f = \dfrac{\int_C fds}{\int_C ds}$.
  3. Consider a wire that lies along the right half of the circle of radius 5 centered at the origin.
    • Give a parametrization for the right half of the circle.
    • The centroid of the wire is the $(\bar x,\bar y)$ location that gives the average $x$ value and $y$ value for points along the wire. Without any integrals, what is $\bar y$?
    • Set up a formula to compute $\bar x$, so set up the integral $\bar f = \dfrac{\int_C x ds}{\int_C ds}$.
    • Compute the integral from the previous part.
  4. For the function $f(x,y)=3x^2+5xy+y^2$, compute both $Df$ and $D^2f$.
  5. Find a function $f(x,y)$ so that $Df(x,y) = \begin{bmatrix}2x+3y&3x+4y\end{bmatrix}.$
  6. Repeat problem 1 using $\vec F = (2x+y,3x)$ for the curve $x=y^2$ from $(1,-1)$ to $(4,2)$.

Problem Set
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